Functionalized polymer

ABSTRACT

A method for providing a polymer having terminal functionality that includes at least one sulfur atom and at least one silicon or tin atom involves reacting a terminally active polymer with a cyclic compound that includes in its ring structure at least one Si or Sn atom and at least one S atom, optionally at adjacent positions of the ring structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a national stage filing under 35 U.S.C. §371 of international application no. PCT/US2010/055824, filed Nov. 8, 2010, which claimed priority to and the benefit of U.S. provisional patent appl. No. 61/261,431, filed Nov. 16, 2009.

BACKGROUND INFORMATION

Rubber goods such as tire treads often are made from elastomeric compositions that contain one or more reinforcing materials such as, for example, particulate carbon black and silica; see, e.g., The Vanderbilt Rubber Handbook, 13th ed. (1990), pp. 603-04.

Good traction and resistance to abrasion are primary considerations for tire treads; however, motor vehicle fuel efficiency concerns argue for a minimization in rolling resistance, which correlates with a reduction in hysteresis and heat build-up during operation of the tire. (A reduction in hysteresis commonly is determined by a decrease in tan δ value at an elevated temperature, e.g., 50° or 60° C. Conversely, good wet traction performance commonly is associated with an increase in tan δ value at a low temperature, e.g., 0° C.)

Reduced hysteresis and traction are, to a great extent, competing considerations: treads made from compositions designed to provide good road traction usually exhibit increased rolling resistance and vice versa.

Filler(s), polymer(s), and additives typically are chosen so as to provide an acceptable compromise or balance of these properties. Ensuring that reinforcing filler(s) are well dispersed throughout the elastomeric material(s) both enhances processability and acts to improve physical properties. Dispersion of fillers can be improved by increasing their interaction with the elastomer(s), which commonly results in reductions in hysteresis (see above). Examples of efforts of this type include high temperature mixing in the presence of selectively reactive promoters, surface oxidation of compounding materials, surface grafting, and chemically modifying the polymer, typically at a terminus thereof.

Various elastomeric materials often are used in the manufacture of vulcanizates such as, e.g., tire components. In addition to natural rubber, some of the most commonly employed include high-cis polybutadiene, often made by processes employing catalysts, and substantially random styrene/butadiene interpolymers, often made by processes employing anionic initiators. Functionalities that can be incorporated into high-cis polybutadiene often cannot be incorporated into anionically initiated styrene/butadiene interpolymers and vice versa.

SUMMARY

In one aspect is provided a method for providing a polymer having terminal functionality which includes at least one sulfur atom and at least one silicon or tin atom. A terminally active polymer is reacted with a cyclic compound so as to provide a polymer having terminal functionality. The cyclic compound includes in its ring structure at least one Si or Sn atom and at least one S atom or S atom-containing moiety which, optionally, can contain one or more additional heteroatoms (e.g., O, N, or P). The ring structure of the cyclic compound also can contain additional S atoms and/or other heteroatoms.

In another aspect is provided a macromolecule that includes at least one polymer chain which includes unsaturated mer units and terminal functionality which includes a S atom and a Si or Sn atom. The terminal functionality is the radical of a cyclic compound that includes in its ring structure at least one Si or Sn atom and at least one S atom.

In the foregoing aspects, the cyclic compound can include at a ring position adjacent the Si or Sn atom a sulfur atom. Additionally or alternatively, the moieties bonded to a ring Si or Sn atom independently can be alkoxy groups, secondary amino groups, or halogen atoms.

In each of the foregoing, some or all of the polymer chains preferably includes polyene mer units. In certain embodiments, the polyenes can be conjugated dienes, and the resulting conjugated diene mer can incorporated substantially randomly along the polymer chain. In each aspect, the polymer can be substantially linear.

The functionalized polymer can interact with particulate filler such as, e.g., carbon black. Compositions, including vulcanizates, that include particulate fillers and such polymers also are provided, as are methods of providing and using such compositions.

Other aspects of the invention will be apparent to the ordinarily skilled artisan from the detailed description that follows. To assist in understanding that description, certain definitions are provided immediately below, and these are intended to apply throughout unless the surrounding text explicitly indicates a contrary intention:

-   -   “polymer” means the polymerization product of one or more         monomers and is inclusive of homo-, co-, ter-, tetra-polymers,         etc.;     -   “mer” or “mer unit” means that portion of a polymer derived from         a single reactant molecule (e.g., ethylene mer has the general         formula —CH₂CH₂—);     -   “copolymer” means a polymer that includes mer units derived from         two reactants, typically monomers, and is inclusive of random,         block, segmented, graft, etc., copolymers;     -   “interpolymer” means a polymer that includes mer units derived         from at least two reactants, typically monomers, and is         inclusive of copolymers, terpolymers, tetra-polymers, and the         like;     -   “substituted” means one containing a heteroatom or functionality         (e.g., hydrocarbyl group) that does not interfere with the         intended purpose of the group in question;     -   “directly bonded” means covalently attached with no intervening         atoms or groups;     -   “polyene” means a molecule, typically a monomer, with at least         two double bonds located in the longest portion or chain         thereof, and specifically is inclusive of dienes, trienes, and         the like;     -   “polydiene” means a polymer that includes mer units from one or         more dienes;     -   “phr” means parts by weight (pbw) per 100 pbw rubber;     -   “radical” means the portion of a molecule that remains after         reacting with another molecule, regardless of whether any atoms         are gained or lost as a result of the reaction;     -   “non-coordinating anion” means a sterically bulky anion that         does not form coordinate bonds with, for example, the active         center of a catalyst system due to steric hindrance;     -   “non-coordinating anion precursor” means a compound that is able         to form a non-coordinating anion under reaction conditions;     -   “ring system” means a single ring or two or more fused rings or         rings linked by a single bond, with the proviso that each ring         includes unsaturation;     -   “terminus” means an end of a polymeric chain;     -   “terminally active” means a polymer with a living or         pseudo-living terminus; and     -   “terminal moiety” means a group or functionality located at a         terminus.

Throughout this document, all values given in the form of percentages are weight percentages unless the surrounding text explicitly indicates a contrary intention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As apparent from the foregoing, the polymer can be described or characterized in a variety of ways. Generally, it includes unsaturated mer units, typically units derived from one or more types of polyenes, and terminal functionality that includes at least one S atom and at least one Si or Sn atom. One S atom and one Si or Sn atom can be at adjacent positions of the ring structure. The Si or Sn atom can be bonded to alkoxy groups, secondary amino groups, halogen atoms or any combination of the foregoing. The polymer can be provided by reacting a terminally active polymer with a cyclic compound that includes in its ring structure at least one S atom and at least one Si or Sn atom.

The polymer can be elastomeric and can include mer units that include ethylenic unsaturation such as those derived from polyenes, particularly dienes and trienes (e.g., myrcene). Illustrative polyenes include C₄-C₁₂ dienes, particularly conjugated dienes such as, but not limited to, 1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2,4-hexadiene, and the like.

Polyenes can incorporate into polymeric chains in more than one way. Especially for tire tread applications, controlling this manner of incorporation can be desirable. A polymer chain with an overall 1,2-microstructure, given as a numerical percentage based on total polyene content, of from ˜10 to ˜80%, optionally from ˜25 to ˜65%, can be desirable for certain end use applications. A polymer that has an overall 1,2-microstructure of no more than ˜50%, preferably no more than ˜45%, more preferably no more than ˜40%, even more preferably no more than ˜35%, and most preferably no more than ˜30%, based on total polyene content, is considered to be “substantially linear”. For certain end use applications, however, keeping the content of 1,2-linkages even lower—e.g., to less than ˜7%, less than 5%, less than 2%, or less than 1%—can be desirable.

Depending on the intended end use, one or more of the polymer chains can include pendent aromatic groups, which can be provided, for example, through incorporation of mer units derived from vinyl aromatics, particularly the C₈-C₂₀ vinyl aromatics such as styrene, α-methyl styrene, p-methyl styrene, the vinyl toluenes, the vinyl naphthalenes, and the like. When used in conjunction with one or more polyenes, mer units with pendent aromatic groups can constitute from ˜1 to ˜50%, from ˜10 to ˜45%, or from ˜20 to ˜35%, of the polymer chain; the microstructure of such interpolymers can be random, i.e., the mer units derived from each type of constituent monomer do not form blocks and, instead, are incorporated in an essentially non-repeating manner. Random microstructure can provide particular benefit in some end use applications such as, e.g., rubber compositions used in the manufacture of tire treads.

Exemplary elastomers include interpolymers of one or more polyenes and styrene such as, e.g., poly(styrene-co-butadiene), also known as SBR.

The number average molecular weight (M_(n)) of the polymer typically is such that a quenched sample exhibits a gum Mooney viscosity (ML₄/100° C.) of from ˜2 to ˜150, more commonly from ˜2.5 to ˜125, even more commonly from ˜5 to ˜100, and most commonly from ˜10 to ˜75.

The foregoing types of polymers can be made by emulsion polymerization or solution polymerization, with the latter affording greater control with respect to such properties as randomness, microstructure, etc. Solution polymerizations have been performed since about the mid-20th century, so the general aspects thereof are known to the ordinarily skilled artisan; nevertheless, certain aspects are provided here for convenience of reference.

Depending on the nature of the polymer desired, the particular conditions of the solution polymerization can vary significantly. In the discussion that follows, living polymerizations are described first followed by a description of coordination catalyst-catalyzed polymerizations. After these descriptions, the functionalization and processing of polymers so made are discussed.

Solution polymerization typically involves an initiator such as an organolithium compound, particularly alkyllithium compounds. Examples of organolithium initiators include N-lithio-hexamethyleneimine; n-butyllithium; tributyltin lithium; dialkylaminolithium compounds such as dimethylaminolithium, diethylaminolithium, dipropylaminolithium, dibutylaminolithium and the like; dialkylaminoalkyllithium compounds such as diethylaminopropyllithium; and those trialkyl stanyl lithium compounds involving C₁-C₁₂, preferably C₁-C₄, alkyl groups.

Multifunctional initiators, i.e., initiators capable of forming polymers with more than one living end, also can be used. Examples of multifunctional initiators include, but are not limited to, 1,4-dilithiobutane, 1,10-dilithiodecane, 1,20-dilithioeicosane, 1,4-dilithiobenzene, 1,4-dilithionaphthalene, 1,10-dilithioanthracene, 1,2-dilithio-1,2-diphenylethane, 1,3,5-trilithiopentane, 1,5,15-trilithioeicosane, 1,3,5-trilithiocyclohexane, 1,3,5,8-tetralithiodecane, 1,5,10,20-tetralithioeicosane, 1,2,4,6-tetralithiocyclohexane, and 4,4′-dilithiobiphenyl.

In addition to organolithium initiators, so-called functionalized initiators also can be useful. These become incorporated into the polymer chain, thus providing a functional group at the initiated end of the chain. Examples of such materials include lithiated aryl thioacetals (see, e.g., U.S. Pat. No. 7,153,919) and the reaction products of organolithium compounds and, for example, N-containing organic compounds such as substituted aldimines, ketimines, secondary amines, etc., optionally pre-reacted with a compound such as diisopropenyl benzene (see, e.g., U.S. Pat. Nos. 5,153,159 and 5,567,815).

Useful anionic polymerization solvents include various C₅-C₁₂ cyclic and acyclic alkanes as well as their alkylated derivatives, certain liquid aromatic compounds, and mixtures thereof. The ordinarily skilled artisan is aware of other useful solvent options and combinations.

In solution polymerizations, both randomization and vinyl content (i.e., 1,2-microstructure) can be increased through inclusion of a coordinator, usually a polar compound, in the polymerization ingredients. Up to 90 or more equivalents of coordinator can be used per equivalent of initiator, with the amount depending on, e.g., the amount of vinyl content desired, the level of non-polyene monomer employed, the reaction temperature, and nature of the specific coordinator employed. Compounds useful as coordinators include organic compounds that include a heteroatom having a non-bonded pair of electrons (e.g., O or N). Examples include dialkyl ethers of mono- and oligo-alkylene glycols; crown ethers; tertiary amines such as tetramethylethylene diamine; THF; THF oligomers; linear and cyclic oligomeric oxolanyl alkanes (see, e.g., U.S. Pat. No. 4,429,091) such as 2,2-bis(2′-tetrahydro-furyl)propane, di-piperidyl ethane, hexamethylphosphoramide, N,N′-dimethylpiperazine, diazabicyclooctane, diethyl ether, tributylamine, and the like.

Although the ordinarily skilled artisan understands the conditions typically employed in solution polymerization, a representative description is provided for convenience of the reader. The following is based on a batch process, although extending this description to, e.g., semi-batch or continuous processes is within the capability of the ordinarily skilled artisan.

Solution polymerization typically begins by charging a blend of monomer(s) and solvent to a suitable reaction vessel, followed by addition of a coordinator (if used) and initiator, which often are added as part of a solution or blend; alternatively, monomer(s) and coordinator can be added to the initiator. The procedure typically is carried out under anhydrous, anaerobic conditions. The reactants can be heated to a temperature of up to ˜150° C. and agitated. After a desired degree of conversion has been reached, the heat source (if used) can be removed and, if the reaction vessel is to be reserved solely for polymerizations, the reaction mixture is removed to a post-polymerization vessel for functionalization and/or quenching. At this point, the reaction mixture commonly is referred to as a “polymer cement” because of its relatively high concentration of polymer.

Generally, polymers made according to anionic techniques can have a M_(n) of from ˜50,000 to ˜500,000 Daltons, although in certain embodiments the number average molecular weight can range from ˜75,000 to ˜250,000 Daltons or even from ˜90,000 to ˜150,000 Daltons.

Certain end use applications call for polymers that have properties that can be difficult or inefficient to achieve via anionic (living) polymerizations. For example, in some applications, conjugated diene polymers having high cis-1,4-linkage contents can be desirable. Polydienes can be prepared by processes using catalysts (as opposed to the initiators employed in living polymerizations) and may display pseudo-living characteristics.

Some catalyst systems preferentially result in cis-1,4-polydienes, while others preferentially provide trans-1,4-polydienes. The ordinarily skilled artisan is familiar with examples of each type of system. The remainder of this description is based on a particular cis-specific catalyst system, although this merely is for sake of exemplification and is not considered to be limiting to the functionalizing method and compounds.

Exemplary catalyst systems can employ lanthanide metals which are known to be useful for polymerizing conjugated diene monomers. Specifically, catalyst systems that include a lanthanide compound can be used to provide cis-1,4-polydienes from one or more types of conjugated dienes.

Preferred lanthanide-based catalyst compositions are described in detail in, for example, U.S. Pat. No. 6,699,813 and patent documents cited therein. The term “catalyst composition” is intended to encompass a simple mixture of ingredients, a complex of various ingredients that is caused by physical or chemical forces of attraction, a chemical reaction product of some or all of the ingredients, or a combination of the foregoing. A condensed description is provided here for convenience and ease of reference.

Exemplary lanthanide catalyst compositions include (a) a lanthanide compound, an alkylating agent and a halogen-containing compound (although use of a halogen-containing compound is optional when the lanthanide compound and/or the alkylating agent contains a halogen atom); (b) a lanthanide compound and an aluminoxane; or (c) a lanthanide compound, an alkylating agent, and a non-coordinating anion or precursor thereof.

Various lanthanide compounds or mixtures thereof can be employed. These compounds preferably are soluble in hydrocarbon solvents such as aromatic hydrocarbons, e.g., benzene, toluene, xylenes, (di)ethylbenzene, mesitylene, and the like; aliphatic hydrocarbons such as linear and branched C₅-C₁₀ alkanes, petroleum ether, kerosene, petroleum spirits, and the like; or cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, and the like; although hydrocarbon-insoluble lanthanide compounds can be suspended in the polymerization medium. Preferred lanthanide compounds include those which include at least one Nd, La, or Sm atom or those including didymium (a commercial mixture of rare-earth elements obtained from monazite sand). The lanthanide atom(s) in the lanthanide compounds can be in any of a number of oxidation states, although compounds having a lanthanide atom in the +3 oxidation state typically are employed. Exemplary lanthanide compounds include carboxylates, organophosphates, organophosphonates, organophosphinates, xanthates, carbamates, dithiocarbamates, β-diketonates, alkoxides, aryloxides, halides, pseudo-halides, oxyhalides, and the like; numerous examples of each of these types of lanthanide compounds can be found in the aforementioned U.S. Pat. No. 6,699,813 as well as other similar patent documents.

Typically, the lanthanide compound is used in conjunction with one or more alkylating agents, i.e., organometallic compounds that can transfer hydrocarbyl groups to another metal. Typically, these agents are organometallic compounds of electropositive metals such as Groups 1, 2, and 3 metals. Exemplary alkylating agents include organoaluminum compounds such as those having the general formula AlR¹ _(n)X_(3-n) (where n is an integer of from 1 to 3 inclusive; each R¹ independently is a monovalent organic group, which may contain heteroatoms such as N, O, B, Si, S, P, and the like, connected to the Al atom via a C atom; and each X independently is a hydrogen atom, a halogen atom, a carboxylate group, an alkoxide group, or an aryloxide group) and oligomeric linear or cyclic aluminoxanes, which can be made by reacting trihydrocarbylaluminum compounds with water, as well as organomagnesium compounds such as those having the general formula R² _(m)MgX_(2-m) where X is defined as above, m is 1 or 2, and R² is the same as R¹ except that each monovalent organic group is connected to the Mg atom via a C atom.

Some catalyst compositions can contain compounds with one or more labile halogen atoms. Preferably, the halogen-containing compounds are soluble in hydrocarbon solvents such as those described above with respect to lanthanide compounds, although hydrocarbon-insoluble compounds can be suspended in the polymerization medium. Useful halogen-containing compounds include elemental halogens, mixed halogens, hydrogen halides, organic halides, inorganic halides, metallic halides, organometallic halides, and mixtures of any two or more of the foregoing.

Other catalyst compositions contain a non-coordinating anion or a non-coordinating anion precursor. Exemplary non-coordinating anions include tetraarylborate anions, particularly fluorinated tetraarylborate anions. Exemplary non-coordinating anion precursors include boron compounds that include strong electron-withdrawing groups.

Catalyst compositions of the type just described have very high catalytic activity for polymerizing conjugated dienes into stereospecific polydienes over a wide range of concentrations and ratios, although polymers having the most desirable properties typically are obtained from systems that employ a relatively narrow range of concentrations and ratios of ingredients. Further, the catalyst ingredients are believed to interact to form an active catalyst species, so the optimum concentration for each ingredient can depend on the concentrations of the other ingredients. The following molar ratios are considered to be relatively exemplary for a variety of different systems based on the foregoing ingredients:

-   -   alkylating agent to lanthanide compound (alkylating agent/Ln):         from ˜1:1 to ˜200:1, preferably from ˜2:1 to ˜100:1, more         preferably from ˜5:1 to ˜50:1;     -   halogen-containing compound to lanthanide compound (halogen         atom/Ln): from ˜1:2 to ˜20:1, preferably from ˜1:1 to ˜10:1,         more preferably from ˜2:1 to ˜6:1;     -   aluminoxane to lanthanide compound, specifically equivalents of         aluminum atoms on the aluminoxane to equivalents of lanthanide         atoms in the lanthanide compound (Al/Ln): from ˜50:1 to         ˜50,000:1, preferably from ˜75:1 to ˜30,000:1, more preferably         from ˜100:1 to ˜1,000:1; and     -   non-coordinating anion or precursor to lanthanide compound         (An/Ln): from ˜1:2 to ˜20:1, preferably from ˜3:4 to ˜10:1, more         preferably from ˜1:1 to ˜6:1.

The molecular weight of polydienes produced with lanthanide-based catalysts can be controlled by adjusting the amount of catalyst used and/or the amounts of co-catalyst concentrations within the catalyst system; polydienes having a wide range of molecular weights can be produced in this manner. In general, increasing the catalyst and co-catalyst concentrations reduces the molecular weight of resulting polydienes, although very low molecular weight polydienes (e.g., liquid polydienes) require extremely high catalyst concentrations. Typically, this necessitates removal of catalyst residues from the polymer to avoid adverse effects such as retardation of the sulfur cure rate. U.S. Pat. No. 6,699,813 teaches that nickel compounds can be used as very efficient molecular weight regulators. Including one or more Ni-containing compounds to lanthanide-based catalyst compositions advantageously permits easy regulation of the molecular weight of the resulting polydiene without significant negative effects on catalyst activity and polymer microstructure.

Various Ni-containing compounds or mixtures thereof can be employed. The Ni-containing compounds preferably are soluble in hydrocarbon solvents such as those set forth above, although hydrocarbon-insoluble Ni-containing compounds can be suspended in the polymerization medium to form the catalytically active species.

The Ni atom in the Ni-containing compounds can be in any of a number of oxidation states including the 0, +2, +3, and +4 oxidation states, although divalent Ni compounds, where the Ni atom is in the +2 oxidation state, generally are preferred. Exemplary Ni compounds include carboxylates, organophosphates, organophosphonates, organophosphinates, xanthates, carbamates, dithiocarbamates, β-diketonates, alkoxides, aryloxides, halides, pseudo-halides, oxyhalides, organonickel compounds (I.e., compounds containing at least one C—Ni bond such as, for example, nickelocene, decamethylnickelocene, etc.), and the like.

The molar ratio of the Ni-containing compound to the lanthanide compound (Ni/Ln) generally ranges from ˜1:1000 to ˜1:1, preferably from ˜1:200 to ˜1:2, and more preferably from ˜1:100 to ˜1:5.

These types of catalyst compositions can be formed using any of the following methods:

-   -   (1) In situ. The catalyst ingredients are added to a solution         containing monomer and solvent (or simply bulk monomer). The         addition can occur in a stepwise or simultaneous manner. In the         case of the latter, the alkylating agent preferably is added         first followed by, in order, the lanthanide compound, the         nickel-containing compound (if used), and (if used) the         halogen-containing compound or the non-coordinating anion or         non-coordinating anion precursor.     -   (2) Pre-mixed. The ingredients can be mixed outside the         polymerization system, generally at a temperature of from about         −20° to ˜80° C., before being introduced to the conjugated diene         monomer(s).     -   (3) Pre-formed in the presence of monomer(s). The catalyst         ingredients are mixed in the presence of a small amount of         conjugated diene monomer(s) at a temperature of from about −20°         to ˜80° C. The amount of conjugated diene monomer can range from         ˜1 to ˜500 moles, preferably from ˜5 to ˜250 moles, and more         preferably from ˜10 to ˜100 moles, per mole of the lanthanide         compound. The resulting catalyst composition is added to the         remainder of the conjugated diene monomer(s) to be polymerized.     -   (4) Two-stage procedure.         -   (a) The alkylating agent is combined with the lanthanide             compound in the absence of conjugated diene monomer, or in             the presence of a small amount of conjugated diene monomer,             at a temperature of from about −20° to ˜80° C.         -   (b) The foregoing mixture and the remaining components are             charged in either a stepwise or simultaneous manner to the             remainder of the conjugated diene monomer(s) to be             polymerized.     -   (The Ni-containing compound, if used, can be included in either         stage.)         When a solution of one or more of the catalyst ingredients is         prepared outside the polymerization system in the foregoing         methods, an organic solvent or carrier is preferably employed.         Useful organic solvents include those mentioned previously.

The production of cis-1,4-polydiene is accomplished by polymerizing conjugated diene monomer(s) in the presence of a catalytically effective amount of a catalyst composition. The total catalyst concentration to be employed in the polymerization mass depends on the interplay of various factors such as the purity of the ingredients, the polymerization temperature, the polymerization rate and conversion desired, the molecular weight desired, and many other factors; accordingly, a specific total catalyst concentration cannot be definitively set forth except to say that catalytically effective amounts of the respective catalyst ingredients should be used. The amount of the lanthanide compound used generally ranges from ˜0.01 to ˜2 mmol, preferably from ˜0.02 to ˜1 mmol, and more preferably from ˜0.05 to ˜0.5 mmol per 100 g conjugated diene monomer. All other ingredients generally are added in amounts that are based on the amount of lanthanide compound (see the various ratios set forth previously).

Polymerization preferably is carried out in an organic solvent, i.e., as a solution or precipitation polymerization where the monomer is in a condensed phase. The catalyst ingredients preferably are solubilized or suspended within the organic liquid. The concentration of monomer present in the polymerization medium at the beginning of the polymerization generally ranges from ˜3 to ˜80%, preferably from ˜5 to ˜50%, and more preferably from ˜10% to ˜30% by weight. (Polymerization also can be carried out by means of bulk polymerization conducted either in a condensed liquid phase or in a gas phase.)

Regardless of whether a batch, continuous, or semi-continuous process is employed, the polymerization preferably is conducted with moderate to vigorous agitation under anaerobic conditions provided by an inert protective gas such as N₂, Ar or He. The polymerization temperature may vary widely, although typically a temperature of from ˜20° to ˜90° C. is employed; heat can be removed by external cooling and/or cooling by evaporation of the monomer or the solvent. The polymerization pressure employed may vary widely, although typically a pressure of from ˜0.1 to ˜1 MPa is employed.

Where 1,3-butadiene is polymerized in a coordination catalyst system, the cis-1,4-polybutadiene generally has a M_(n), as determined by GPC using polystyrene standards, of from ˜5,000 to ˜200,000 Daltons, from ˜25,000 to ˜150,000 Daltons, or from ˜50,000 to ˜120,000 Daltons. The polydispersity of the polymers generally ranges from ˜1.5 to ˜5.0, typically from ˜2.0 to ˜4.0.

Resulting polydienes advantageously can have a cis-1,4-linkage content of at least ˜60%, at least ˜75%, at least ˜90%, and even at least ˜95%, and a 1,2-linkage content of less than ˜7%, less than ˜5%, less than ˜2%, and even less than ˜1%.

Both of the described polymerization processes advantageously result in polymer chains that possess reactive (living or pseudo-living) terminals, which can be further reacted with one or more functionalizing agents so as to provide functionalized polymers. As described above, functionalization can enhance the interaction between the polymer and particulate fillers in rubber compounds, thereby improving the mechanical and dynamic properties of the resulting vulcanizates.

As mentioned above, the polymer includes terminal functionality. This polymer, hereinafter referred to as the functionalized polymer, can be provided by reacting a terminally active polymer with a cyclic compound that includes in its ring structure at least one S atom and at least one Si or Sn atom. The ring structure can involve from 5 to ˜20 atoms, preferably from 5 to 15 atoms, more preferably from 5 to 10 atoms, and most preferably from 5 to 7 atoms. (Where the ring structure involves from 8 to 20 atoms, it can involve two or more rings, and these rings optionally can be fused.)

In addition to the aforementioned heteroatoms, the cyclic compound can include any atoms or groups that do not interfere with its intended purposes including, of relevance here, an ability to ring open in the presence of, and attach to, terminally active polymers. Included among the types of atoms that can be included are heteroatoms including O, N and/or P. The cyclic compound also can include more than one S atom and/or more than one Si or Sn atom.

Silicon and tin atoms typically are tetravalent, so any Si or Sn atom in a ring structure is bonded to two additional substitutents. In the compounds at issue here, these groups should not interfere with the ability to form the desired functionalized polymer. Exemplary substituents include monovalent organic groups, particularly alkoxy groups (preferably C₁-C₂₀, more preferably C₁-C₆, alkoxy groups), secondary amino groups (preferably those having C₁-C₂₀, more preferably C₂-C₁₀ alkyl substituents) and halogen atoms.

In the cyclic compound, one sulfur atom and one silicon or tin atom can occupy adjacent positions on the ring structure. A non-exclusive class of useful cyclic compounds of this type can be defined by the formula

where M represents a silicon or tin atom; each R³ independently is a monovalent organic group, preferably an alkoxy group, a secondary amine group, or a halogen atom; each R⁴ independently is a hydrogen atom or a monovalent organic group, particularly a monovalent hydrocarbyl group which optionally can contain one or more heteroatoms (e.g., O, S, N, P, Si, Sn, etc.) or heteroatom-containing group, with the proviso that such group not contain any active H atoms (i.e., does not produce methane when subjected to Zerewitinoff determination testing); and n is an integer of from 1 to about 16 inclusive, preferably from 1 to 6 inclusive, and more preferably from 1 to 3 inclusive. Many such compounds are available from commercial sources such as Gelest, Inc. (Morrisville, Pa.). These and others can be synthesized by, for example, introducing a compound of the general formula HS—(CH₂)_(n)—SiR³ ₂ to a base such as an alkali metal hydride.

One sulfur atom need not occupy a ring position adjacent a silicon or tin atom in the cyclic compound. Non-limiting examples of cyclic compounds where a S atom does not occupy a ring position adjacent a Si or Sn atom include

where R³ is defined as above. From these two non-limiting examples, the ordinarily skilled artisan can envision other similar compounds.

Reaction of these types of compounds with a terminally active polymer can be performed relatively quickly (a few minutes to a few hours) at moderate temperatures (e.g., 0° to 75° C.). Bonding typically occurs between a C atom of the terminally active portion of the polymer chain and a Si or Sn atom of the (ring opened) cyclic compound, with one of the substituents of the Si or Sn atom optionally acting as a leaving group.

Although typically not required, if desired, quenching can be conducted by stirring the polymer and an active hydrogen-containing compound, such as an alcohol or acid, for up to ˜120 minutes at temperatures of from ˜25° to ˜150° C.

Solvent can be removed from the quenched polymer cement by conventional techniques such as drum drying, extruder drying, vacuum drying or the like, which may be combined with coagulation with water, alcohol or steam, thermal desolvation, etc.; if coagulation is performed, oven drying may be desirable.

The resulting polymer can be utilized in a tread stock compound or can be blended with any conventionally employed tread stock rubber including natural rubber and/or non-functionalized synthetic rubbers such as, e.g., one or more of homo- and interpolymers that include just polyene-derived mer units (e.g., poly(butadiene), poly(isoprene), and copolymers incorporating butadiene, isoprene, and the like), SBR, butyl rubber, neoprene, EPR, EPDM, acrylonitrile/butadiene rubber (NBR), silicone rubber, fluoroelastomers, ethylene/acrylic rubber, EVA, epichlorohydrin rubbers, chlorinated polyethylene rubbers, chlorosulfonated polyethylene rubbers, hydrogenated nitrile rubber, tetrafluoroethylene/propylene rubber and the like. When a functionalized polymer(s) is blended with conventional rubber(s), the amounts can vary from ˜5 to ˜99% of the total rubber, with the conventional rubber(s) making up the balance of the total rubber. The minimum amount depends to a significant extent on the degree of hysteresis reduction desired.

Amorphous silica (SiO₂) can be utilized as a filler. Silicas are generally classified as wet-process, hydrated silicas because they are produced by a chemical reaction in water, from which they are precipitated as ultrafine, spherical particles. These primary particles strongly associate into aggregates, which in turn combine less strongly into agglomerates. “Highly dispersible silica” is any silica having a very substantial ability to de-agglomerate and to disperse in an elastomeric matrix, which can be observed by thin section microscopy.

Surface area gives a reliable measure of the reinforcing character of different silicas; the Brunauer, Emmet and Teller (“BET”) method (described in J. Am. Chem. Soc., vol. 60, p. 309 et seq.) is a recognized method for determining surface area. BET surface area of silicas generally is less than 450 m²/g, and useful ranges of surface include from ˜32 to ˜400 m²/g, ˜100 to ˜250 m²/g, and ˜150 to ˜220 m²/g.

The pH of the silica filler is generally from ˜5 to ˜7 or slightly over, preferably from ˜5.5 to ˜6.8.

Some commercially available silicas which may be used include Hi-Sil™ 215, Hi-Sil™ 233, and Hi-Sil™190 (PPG Industries, Inc.; Pittsburgh, Pa.). Other suppliers of commercially available silica include Grace Davison (Baltimore, Md.), Degussa Corp. (Parsippany, N.J.), Rhodia Silica Systems (Cranbury, N.J.), and J.M. Huber Corp. (Edison, N.J.).

Silica can be employed in the amount of ˜1 to ˜100 phr, preferably in an amount from ˜5 to ˜80 phr. The useful upper range is limited by the high viscosity that such fillers can impart.

Other useful fillers include all forms of carbon black including, but not limited to, furnace black, channel blacks and lamp blacks. More specifically, examples of the carbon blacks include super abrasion furnace blacks, high abrasion furnace blacks, fast extrusion furnace blacks, fine furnace blacks, intermediate super abrasion furnace blacks, semi-reinforcing furnace blacks, medium processing channel blacks, hard processing channel blacks, conducting channel blacks, and acetylene blacks; mixtures of two or more of these can be used. Carbon blacks having a surface area (EMSA) of at least 20 m²/g, preferably at least ˜35 m²/g, are preferred; surface area values can be determined by ASTM D-1765 using the CTAB technique. The carbon blacks may be in pelletized form or an unpelletized flocculent mass, although unpelletized carbon black can be preferred for use in certain mixers.

The amount of carbon black can be up to ˜50 phr, with ˜5 to ˜40 phr being typical. When carbon black is used with silica, the amount of silica can be decreased to as low as ˜1 phr; as the amount of silica decreases, lesser amounts of the processing aids, plus silane if any, can be employed.

Elastomeric compounds typically are filled to a volume fraction, which is the total volume of filler(s) added divided by the total volume of the elastomeric stock, of ˜25%; accordingly, typical (combined) amounts of reinforcing fillers, i.e., silica and carbon black, is ˜30 to 100 phr.

When silica is employed as a reinforcing filler, addition of a coupling agent such as a silane is customary so as to ensure good mixing in, and interaction with, the elastomer(s). Generally, the amount of silane that is added ranges between ˜4 and 20%, based on the weight of silica filler present in the elastomeric compound.

Coupling agents can have a general formula of A-T-G, in which A represents a functional group capable of bonding physically and/or chemically with a group on the surface of the silica filler (e.g., surface silanol groups); T represents a hydrocarbon group linkage; and G represents a functional group capable of bonding with the elastomer (e.g., via a sulfur-containing linkage). Such coupling agents include organosilanes, in particular polysulfurized alkoxysilanes (see, e.g., U.S. Pat. Nos. 3,873,489, 3,978,103, 3,997,581, 4,002,594, 5,580,919, 5,583,245, 5,663,396, 5,684,171, 5,684,172, 5,696,197, etc.) or polyorganosiloxanes bearing the G and A functionalities mentioned above. An exemplary coupling agent is bis[3-(tri-ethoxysilyl)propyl]tetrasulfide.

Addition of a processing aid can be used to reduce the amount of silane employed. See, e.g., U.S. Pat. No. 6,525,118 for a description of fatty acid esters of sugars used as processing aids. Additional fillers useful as processing aids include, but are not limited to, mineral fillers, such as clay (hydrous aluminum silicate), talc (hydrous magnesium silicate), and mica as well as non-mineral fillers such as urea and sodium sulfate. Preferred micas contain principally alumina, silica and potash, although other variants also can be useful. The additional fillers can be utilized in an amount of up to ˜40 phr, typically up to ˜20 phr.

Other conventional rubber additives also can be added. These include, for example, process oils, plasticizers, anti-degradants such as antioxidants and antiozonants, curing agents and the like.

All of the ingredients can be mixed using standard equipment such as, e.g., Banbury or Brabender mixers. Typically, mixing occurs in two or more stages. During the first stage (often referred to as the masterbatch stage), mixing typically is begun at temperatures of ˜120° to ˜130° C. and increases until a so-called drop temperature, typically ˜165° C., is reached.

Where a formulation includes silica, a separate re-mill stage often is employed for separate addition of the silane component(s). This stage often is performed at temperatures similar to, although often slightly lower than, those employed in the masterbatch stage, i.e., ramping from ˜90° C. to a drop temperature of ˜150° C.

Reinforced rubber compounds conventionally are cured with ˜0.2 to ˜5 phr of one or more known vulcanizing agents such as, for example, sulfur or peroxide-based curing systems. For a general disclosure of suitable vulcanizing agents, the interested reader is directed to an overview such as that provided in Kirk-Othmer, Encyclopedia of Chem. Tech., 3d ed., (Wiley Interscience, New York, 1982), vol. 20, pp. 365-468. Vulcanizing agents, accelerators, etc., are added at a final mixing stage. To ensure that onset of vulcanization does not occur prematurely, this mixing step often is done at lower temperatures, e.g., starting at ˜60° to ˜65° C. and not going higher than ˜105° to ˜110° C.

The following non-limiting, illustrative examples provide the reader with detailed conditions and materials that can be useful in the practice of the present invention.

EXAMPLES

In the following examples, dried glass vessels previously sealed with extracted septum liners and perforated crown caps under a positive N₂ purge were used for all preparations unless otherwise indicated. Butadiene solution (21.9% in hexane), styrene solution (33% in hexane), hexane, n-butyllithium (1.60 M in hexane), 2,2-bis(2′-tetrahydrofuryl)-propane (1.60 M solution in hexane, stored over CaH₂), and butylated hydroxytoluene (BHT) solution in hexane were used.

Commercially available reagents and starting materials included the following, all of which were used without further purification unless otherwise noted in a specific example: N-(n-butyl)-aza-2,2-dimethoxysilacyclopentane and 2,2-dimethoxy-1-thia-2-silacyclopentane (from Gelest, Inc.) and hexamethyleneimine (“HMI,” 99% purity, from Sigma-Aldrich Co.; St. Louis, Mo.).

Example 1 Control Interpolymer

To a N₂-purged reactor equipped with a stirrer was added 1.59 kg hexane, 0.41 kg styrene solution, and 2.49 kg butadiene solution. The reactor was charged with 3.30 mL n-butyllithium solution, followed by 1.1 mL 2,2-bis(2′-tetrahydrofuryl)propane solution. The reactor jacket was heated to 50° C. and, after ˜27 minutes, the batch temperature peaked at ˜63° C. After an additional ˜30 minutes, polymer cement was dropped into isopropanol containing BHT. Coagulated polymer was drum dried. Properties of this polymer (sample 1) are summarized below in Table 1.

Examples 2-3 Functionalized Interpolymers

The procedure from Example 1 was essentially repeated. After adding identical amounts of reagents, the reactor then was charged with 3.27 mL n-butyllithium solution, followed by 1.1 mL 2,2-bis(2′-tetrahydrofuryl)propane solution. The reactor jacket was heated to 50° C. and, after ˜25 minutes, the batch temperature peaked at ˜62° C. After an additional ˜30 minutes, 5.3 mL 2,2-dimethoxy-1-thia-2-silacyclopentane (DMTSCP) solution (1.0 M in hexane) was added, and the composition was agitated at 50° C. for additional ˜30 minutes. This functionalized polymer (sample 2) was coagulated and drum dried similarly to the control polymer from Example 1.

The procedure from Example 1 again was essentially repeated. After adding identical amounts of reagents, the reactor was charged with 1.57 mL HMI (3.0 M in hexane) followed by 3.27 mL n-butyllithium solution. After 5 minutes agitation at room temperature, 1.1 mL 2,2-bis(2′-tetrahydrofuryl)propane solution was added. The reactor jacket was heated to 50° C. and, after ˜27 minutes, the batch temperature peaked at ˜63° C. After an additional ˜30 minutes, 5.3 mL DMTSCP solution (1.0 M in hexane) was added, and the composition was agitated at 50° C. for additional ˜30 minutes. This functionalized polymer (sample 3) was coagulated and drum dried similarly to the control polymer from Example 1.

Properties of these functionalized interpolymers, along with those of the non-functionalized control (sample 1), are summarized below in the following table.

TABLE 1 Properties of polymers from Examples 1-3 1 2 3 M_(n) (kg/mol) 119.7 145.8 145.9 M_(w)/M_(n) 1.04 1.18 1.23 M_(p) (kg/mol) 128.9 132.3 127.6 T_(g) (° C.) −37.8 −35.1 −38.3 % coupling 0 30.8 36.9

Examples 4-6 Filled Compositions and Vulcanizates

The polymers from Examples 1-3 were used to make filled compositions (compounds), employing the formulation shown in Table 2a (carbon black as sole particulate filler) and Table 2b (silica as sole particulate filler) where N-phenyl-N′-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD) acts as an antioxidant and 2,2′-dithiobis(benzothiazole) (MBTS), N-tert-butylbenzothiazole-2-sulfenamide (TBBS) and N,N′-diphenylguanidine (DPG) act as accelerators. Black oil is an extender oil that contains a relatively low amount of polycyclic aromatic compounds.

TABLE 2a Carbon black compound formulation Amount (phr) Masterbatch synthesized polymer 100 carbon black (N343 type) 50 wax 2 6PPD 0.95 stearic acid 2 black oil 10 Final sulfur 1.5 ZnO 2.5 TBBS 0.5 MBTS 0.5 DPG 0.3 TOTAL 170.25

TABLE 2b Silica compound formulation Amount (phr) Masterbatch synthetic polymer 80 natural rubber 20 silica 52.5 wax 2 6PPD 0.95 stearic acid 2 black oil 10 Re-mill 60% disulfide silane on carrier 5 silica 2.5 Final sulfur 1.5 ZnO 2.5 MBTS 2 TBBS 0.7 DPG 1.4 TOTAL 183.05

Compounds were cured for ˜15 minutes at 171° C. Results of physical testing on these compounds are shown below in Table 3a (carbon black) and 3b (silica).

Results of physical testing on vulcanizates made from these polymers also are summarized below in Tables 3a and 3b. For the “Temp. sweep” line, the top row of data are from measurements at 0° C. while the bottom row are from measurements at 60° C.

Mooney viscosity (ML₁₊₄) values were determined with an Alpha Technologies™ Mooney viscometer (large rotor) using a one-minute warm-up time and a four-minute running time; tensile mechanical properties were determined using the standard procedure described in ASTM-D412; Payne effect (ΔG′, i.e., the difference between G′ at 0.25% strain and at 14% strain) and hysteresis (tan δ) data were obtained from dynamic experiments conducted at 60° C. and 10 Hz (strain sweep) and 2% strain and 10 Hz (temperature sweep). With respect to tensile properties, M_(X) is modulus at X % elongation, T_(b) is tensile strength at break, and E_(b) is percent elongation at break.

TABLE 3a Compound and vulcanizate properties (carbon black) 4 5 6 synthetic polymer (sample no.) 1 2 3 MDR2000 @ 171° C. (final) ML (kg · cm) 0.91 4.01 2.02 MH (kg · cm) 17.19 16.63 16.44 t₉₀ (min) 6.52 5.71 4.06 ML₁₊₄ @ 100° C. (final) 44.2 96.0 93.3 Tensile @ 23° C. (final, unaged) M₅₀ (MPa) 1.65 1.62 1.44 M₃₀₀ (MPa) 11.64 18.16 13.52 T_(b) (MPa) 16.3 18.8 16.4 E_(b) (%) 393 308 360 Tensile @ 100° C. (final, unaged) M₅₀ (MPa) 1.28 1.49 1.37 M₂₀₀ (MPa) 5.65 9.14 7.62 T_(b) (MPa) 8.0 9.8 7.5 E_(b) (%) 262 211 199 Strain sweep (60° C., 10 Hz, final) G′ @ 5% strain (MPa) 2.678 2.293 1.905 G″ @ 5% strain (MPa) 0.593 0.328 0.170 tan δ @ 5% strain 0.2213 0.1428 0.0891 ΔG′ (MPa) 3.431 1.312 0.437 Temp. sweep (2% strain, 10 Hz, final) G′ (MPa) 15.535 10.803 5.871 5.590 4.062 3.152 G″ (MPa) 6.132 5.169 2.509 1.214 0.584 2.877 tan δ 0.3944 0.4781 0.4274 0.2171 0.1438 0.0913 Dynastat tan δ (60° C., final) 0.2068 0.1340 0.909 Bound rubber (%) 9.6 54.1 22.6

TABLE 3b Compound and vulcanizate properties (silica) 4 5 6 synthetic polymer (sample no.) 1 2 3 MDR2000 @ 171° C. (final) ML (kg · cm) 1.75 3.11 2.82 MH (kg · cm) 24.43 21.36 25.40 t₉₀ (min) 6.26 5.32 5.30 ML₁₊₄ @ 100° C. (final) 43.0 82.6 85.3 Tensile @ 23° C. (final, unaged) M₅₀ (MPa) 1.80 1.53 2.11 M₃₀₀ (MPa) 13.58 15.27 14.30 T_(b) (MPa) 15.4 16.7 15.7 E_(b) (%) 330 318 323 Tensile @ 100° C. (final, unaged) M₅₀ (MPa) 1.66 1.45 1.87 M₂₀₀ (MPa) 6.91 8.00 8.07 T_(b) (MPa) 7.3 7.3 7.7 E_(b) (%) 206 191 191 Strain sweep (60° C., 10 Hz, final) G′ @ 5% strain (MPa) 4.528 2.537 2.607 G″ @ 5% strain (MPa) 0.659 0.228 0.227 tan δ @ 5% strain 0.1454 0.0899 0.0870 ΔG′ (MPa) 5.282 1.130 1.106 Temp. sweep (2% strain, 10 Hz, final) G′ (MPa) 14.674 9.514 13.404 7.527 4.546 6.775 G″ (MPa) 4.883 3.725 4.488 0.946 0.397 0.667 tan δ 0.3324 0.3881 0.3324 0.1256 0.0873 0.0985 Dynastat tan δ (60° C., final) 0.1139 0.0752 0.0704 Bound rubber (%) 14.0 47.8 38.7

While the data of Tables 3a and 3b include much of interest, one line of particular interest is the 60° C. strain sweep tan δ data, where vulcanizates employing interpolymers having terminal radicals derived from cyclic compounds falling within formula (I) above are seen to exhibit significant reductions in tan δ compared to a vulcanizate employing a control SBR. The presence of a functionalized initiator can reinforce or enhance this reduction.

More complete sets of strain sweep test results and temperature sweep test results are tabulated in, respectively, Tables 4 and 5 below.

TABLE 4 Results (tan δ) of strain sweep testing @ 60° C. 4 5 6 Strain (%) (sample 1) (sample 2) (sample 3) 0.249 0.0708 0.0575 0.0597 0.497 0.0859 0.0602 0.0621 0.745 0.0993 0.0647 0.0644 0.994 0.1091 0.0686 0.0674 1.243 0.1164 0.0726 0.0703 1.491 0.1221 0.0757 0.0714 1.738 0.1263 0.0786 0.0727 1.987 0.1297 0.0805 0.0741 2.236 0.1325 0.0823 0.0751 2.486 0.1347 0.0837 0.0760 2.735 0.1366 0.0849 0.0768 2.984 0.1383 0.0859 0.0775 3.230 0.1396 0.0867 0.0779 3.479 0.1407 0.0875 0.0783 3.727 0.1417 0.0882 0.0787 3.977 0.1428 0.0886 0.0792 4.226 0.1435 0.0891 0.0795 4.476 0.1442 0.0894 0.0797 4.726 0.1448 0.0896 0.0799 4.971 0.1454 0.0899 0.0801 5.471 0.1464 0.0903 0.0805 5.969 0.1468 0.0906 0.0806 6.464 0.1473 0.0908 0.0809 6.963 0.1476 0.0909 0.0811 7.463 0.1478 0.0909 0.0813 7.957 0.1480 0.0911 0.0814 8.458 0.1478 0.0911 0.0815 8.957 0.1477 0.0912 0.0817 9.452 0.1476 0.0910 0.0817 9.951 0.1472 0.0909 0.0817 10.449 0.1467 0.0909 0.0817 10.950 0.1467 0.0907 0.0818 11.445 0.1463 0.0905 0.0818 11.944 0.1460 0.0904 0.0817 12.938 0.1449 0.0901 0.0817 13.940 0.1440 0.0898 0.0817 14.183 0.1438 0.0896 0.0817 14.432 0.1435 0.0896 0.0815

TABLE 5 Results (tan δ) of temperature sweep testing @ 2% strain Temp. 4 5 6 (° C.) (sample 1) (sample 2) (sample 3) −79.75 0.0167 0.0182 0.0181 −65.74 0.0218 0.0224 0.0208 −60.22 0.0371 0.0404 0.0342 −55.94 0.0587 0.0613 0.0545 −50.37 0.0780 0.0735 0.0715 −46.38 0.0817 0.0794 0.0760 −40.17 0.1062 0.1223 0.1088 −36.50 0.1588 0.2013 0.1686 −30.52 0.3777 0.4711 0.3986 −26.59 0.6103 0.7315 0.6269 −22.94 0.7515 0.8472 0.7652 −20.63 0.7276 0.8154 0.7413 −14.61 0.4943 0.5894 0.5285 −10.79 0.3714 0.4660 0.4045 −5.61 0.4179 0.4632 0.4267 −0.23 0.3353 0.3658 0.3391 4.37 0.2788 0.2908 0.2764 8.96 0.2403 0.2366 0.2309 13.83 0.2115 0.1994 0.1994 18.72 0.1929 0.1713 0.1771 23.51 0.1787 0.1516 0.1607 28.78 0.1674 0.1371 0.1472 33.68 0.1605 0.1257 0.1365 38.80 0.1537 0.1156 0.1270 43.55 0.1471 0.1064 0.1185 48.41 0.1397 0.0983 0.1103 53.43 0.1325 0.0913 0.1041 58.33 0.1271 0.0867 0.0995 63.63 0.1224 0.0825 0.0955 68.52 0.1192 0.0790 0.0906 73.40 0.1157 0.0763 0.0878 78.07 0.1124 0.0736 0.0850 83.69 0.1089 0.0706 0.0816 93.82 0.1041 0.0654 0.0779 98.82 0.1011 0.0638 0.0758

Examples 7-9 Interpolymers

The synthesis procedure described above in Example 1 was essentially repeated. One portion of the interpolymer was terminated with isopropanol (sample 7 below), while two others were reacted with, respectively, DMTSCP (sample 8 below) and N-(n-butyl)-aza-2,2-dimethoxy-silacyclopentane (sample 9 below). (Use of the azasilacycloalkane to provide terminal functionality is described in U.S. Pat. No. 7,504,457, so sample 9 is a comparative.) These polymers were collected and processed as described in previous examples.

Cold flow testing was performed using a Scott™ tester (PTES Equipment Services, Inc.; Johnston, R.I.). Samples were prepared by melt pressing 2.5 g of polymer at 100° C. for 20 minutes in a mold using a preheated press. The resulting cylindrical samples, which had a uniform thickness of ˜12 mm, were allowed to cool to room temperature before being removed from the mold. Samples were placed individually under the weight of a 5 kg calibrated weight. Tests were conducted for ˜30 min. (measured from time that the weight was released), with sample thicknesses being recorded as a function of time. Sample thickness at the conclusion of ˜30 min. generally is considered to be an acceptable indicator of resistance to cold flow for this type of polymer.

Properties of the polymers from samples 7-9 are summarized in the following table, the data of which indicate significantly improved cold flow performance of a functionalized interpolymer according to the present invention (sample 8) relative to a non-functionalized interpolymer of similar composition and microstructure (sample 7).

TABLE 6 Properties of polymers from Examples 7-9 7 8 9 M_(n) (kg/mol) 139.0 247.3 195.9 T_(g) (° C.) −33.9 −33.0 −35.9 % coupling 2.6 90.8 60.7 Cold flow (mm) 2.6 4.6 6.8

Examples 10-12 Compounds and Vulcanizates

Using the formulation from Table 2b above, polymer samples 7-9 were used to make filled compositions. Vulcanizates 10-12 were prepared from these compositions, using the procedure set forth above in connection with Examples 4-6.

Results of testing on these vulcanizates are set forth in the following table. Data corresponding to “Dispersion index” (DI) were calculated using the equation DI=100−exp[A×log₁₀(F ² H)+B] where F is the number of roughness peaks/cm, H is the average roughness peak height, and A and B are constants from Method B in ASTM-D 2663-89. The F and H contour data were acquired by analyzing cut samples (˜3.5×2×0.2 cm) with a Surfanalyzer™ profilometer (Mahr Federal Inc.; Providence, R.I.), using the procedure described in Method C (from ASTM-D 2663-89).

TABLE 7 Compound and vulcanizate properties (silica) 10 11 12 synthetic polymer (sample no.) 7 8 9 DI 71.3 66.9 85.7 MDR2000 @ 171° C. (final) ML (kg · cm) 1.67 1.59 3.44 MH (kg · cm) 24.70 25.98 20.88 t₉₀ (min) 6.74 6.53 5.65 ML₁₊₄ @ 100° C. (final) 19.9 63.3 50.0 Tensile @ 23° C. (final, unaged) M₅₀ (MPa) 1.51 1.24 1.57 M₃₀₀ (MPa) 8.12 8.95 16.37 T_(b) (MPa) 11.6 14.1 16.9 E_(b) (%) 392 405 308 Tensile @ 100° C. (final, unaged) M₅₀ (MPa) 1.39 1.23 1.46 M₂₀₀ (MPa) 4.68 4.89 — T_(b) (MPa) 7.0 6.9 6.8 E_(b) (%) 284 259 178 Strain sweep (60° C., 10 Hz, final) G′ @ 5% strain (MPa) 3.598 2.289 2.450 G″ @ 5% strain (MPa) 0.556 0.179 0.196 tan δ @ 5% strain 0.1546 0.0783 0.0801 ΔG′ (MPa) 3.868 0.626 0.769 Temp. sweep (2% strain, 10 Hz, final) G′ (MPa) 15.544 7.261 5.897 7.682 3.694 4.117 G″ (MPa) 5.635 3.357 2.327 0.923 0.245 0.280 tan δ 0.3603 0.4577 0.3846 0.1201 0.0662 0.0680 Peak tan δ 0.7759 0.9835 0.9423 Dynastat tan δ (60° C., final) 0.1197 0.0669 0.0680 Bound rubber (%) 18.7 79.3 68.0

While the data of Table 7 include much of interest, one line of particular interest is the 60° C. strain sweep tan δ data, where vulcanizates employing interpolymers having terminal radicals derived from cyclic compounds falling within formula (I) above are seen to exhibit significant reductions in tan δ compared to a vulcanizate employing a control SBR. This is an indication of increased interaction between the polymer chain and the particulate filler.

A more complete set of strain sweep test results and temperature sweep test results are tabulated in, respectively, Tables 8 and 9 below.

TABLE 8 Results of strain sweep testing @ 60° C. 10 11 12 Strain (sample 7) (sample 8) (sample 9) (%) tan δ G′ (MPa) tan δ G′ (MPa) tan δ G′ (MPa) 0.248 0.0757 6.59 0.0605 2.65 0.0597 2.89 0.497 0.0928 6.13 0.0625 2.62 0.0621 2.85 0.746 0.1092 5.69 0.0643 2.59 0.0644 2.81 0.994 0.1218 5.34 0.0667 2.56 0.0674 2.78 1.243 0.1305 5.07 0.0688 2.53 0.0703 2.76 1.492 0.1369 4.85 0.0704 2.51 0.0714 2.71 1.739 0.1417 4.67 0.0721 2.49 0.0727 2.68 1.990 0.1454 4.52 0.0733 2.46 0.0741 2.66 2.237 0.1481 4.39 0.0742 2.44 0.0751 2.63 2.485 0.1500 4.28 0.0750 2.43 0.0760 2.61 2.735 0.1515 4.18 0.0759 2.41 0.0768 2.59 2.983 0.1526 4.09 0.0762 2.39 0.0775 2.57 3.234 0.1535 4.01 0.0768 2.38 0.0779 2.55 3.481 0.1542 3.93 0.0770 2.36 0.0783 2.54 3.728 0.1544 3.87 0.0774 2.35 0.0787 2.52 3.978 0.1549 3.81 0.0775 2.34 0.0792 2.51 4.227 0.1548 3.75 0.0778 2.32 0.0795 2.49 4.477 0.1552 3.70 0.0779 2.31 0.0797 2.48 4.724 0.1552 3.65 0.0778 2.30 0.0799 2.46 4.974 0.1547 3.60 0.0783 2.29 0.0801 2.45 5.471 0.1539 3.52 0.0781 2.27 0.0805 2.43 5.970 0.1531 3.45 0.0786 2.25 0.0806 2.40 6.469 0.1520 3.39 0.0784 2.23 0.0809 2.38 6.962 0.1510 3.33 0.0782 2.21 0.0811 2.36 7.465 0.1496 3.28 0.0785 2.19 0.0813 2.34 7.963 0.1483 3.23 0.0787 2.18 0.0814 2.32 8.459 0.1467 3.19 0.0783 2.16 0.0815 2.30 8.955 0.1456 3.15 0.0781 2.15 0.0817 2.28 9.457 0.1443 3.10 0.0778 2.13 0.0817 2.26 9.953 0.1434 3.06 0.0783 2.12 0.0817 2.25 10.451 0.1424 3.02 0.0781 2.11 0.0817 2.23 10.954 0.1417 2.98 0.0775 2.09 0.0818 2.21 11.448 0.1411 2.93 0.0777 2.08 0.0818 2.20 11.944 0.1408 2.89 0.0776 2.07 0.0817 2.18 12.941 0.1397 2.80 0.0775 2.04 0.0817 2.15 13.938 0.1387 2.73 0.0770 2.02 0.0817 2.13 14.431 0.1385 2.69 0.0769 2.01 0.0815 2.11

TABLE 9 Results (tan δ) of temperature sweep testing @ 2% strain Temp. 10 11 12 (° C.) (sample 7) (sample 8) (sample 9) −79.33 0.0193 0.0200 0.0169 −71.16 0.0188 0.0191 0.0175 −65.32 0.0222 0.0222 0.0216 −61.47 0.0302 0.0294 0.0307 −55.65 0.0581 0.0568 0.0615 −53.66 0.0681 0.0661 0.0718 −51.53 0.0743 0.0709 0.0777 −45.51 0.0787 0.0745 0.0809 −39.52 0.0942 0.0984 0.1094 −35.58 0.1306 0.1442 0.1756 −29.77 0.2942 0.3275 0.4386 −25.79 0.5130 0.5649 0.7220 −23.72 0.6421 0.7143 0.8530 −19.70 0.7759 0.9578 0.9369 −17.83 0.7439 0.9833 0.8837 −15.70 0.6667 0.9455 0.8073 −9.61 0.4235 0.6912 0.5547 −4.44 0.4416 0.5963 0.4885 0.66 0.3482 0.4393 0.3496 5.48 0.2838 0.3251 0.2814 10.27 0.2380 0.2442 0.2195 15.01 0.2074 0.1908 0.1751 20.15 0.1857 0.1548 0.1474 25.22 0.1716 0.1299 0.1264 30.27 0.1600 0.1112 0.1112 35.54 0.1522 0.0991 0.0999 40.11 0.1444 0.0886 0.0910 45.19 0.1366 0.0795 0.0847 50.39 0.1303 0.0735 0.0771 55.55 0.1239 0.0679 0.0722 60.45 0.1197 0.0661 0.0677 65.45 0.1149 0.0636 0.0636 75.79 0.1085 0.0573 0.0590 85.28 0.1011 0.0533 0.0552 95.50 0.0954 0.0487 0.0517

Tables 6 and 7 show that vulcanizates employing functionalized SBR interpolymers exhibit significant reductions in hysteresis relative to compounds employing a control SBR. Similar positive trends can be seen in the G′ data of these tables. 

What is claimed is:
 1. A method for providing a polymer having terminal functionality, said method comprising reacting a terminally active polymer with a cyclic compound that comprises in its ring structure one or more sulfur atoms and one or more M atoms where M is silicon or tin, thereby providing said polymer having terminal functionality, wherein at least one of said one or more M atoms is bonded to at least one halogen atom or a secondary amine group.
 2. The method of claim 1 wherein at least one of said M atoms is bonded to at least one alkoxy group.
 3. The method of claim 1 wherein said cyclic compound is defined by the formula

where M is a silicon or tin atom; each R³ independently is a monovalent organic group or a halogen atom with the proviso that at least one R³ is a secondary amine group or a halogen atom; each R⁴ independently is a hydrogen atom or a monovalent organic group that is free of active H atoms; and n is an integer of from 1 to about 16 inclusive.
 4. The method of claim 3 wherein one R³ is an alkoxy group.
 5. The method of claim 4 wherein one R³ is a secondary amine group.
 6. The method of claim 4 wherein one R³ is a halogen atom.
 7. The method of claim 3 wherein n is an integer of from 1 to 6 inclusive.
 8. The method of claim 3 wherein n is an integer of from 1 to 3 inclusive.
 9. The method of claim 3 wherein M is a silicon atom and one R³ is an alkoxy group.
 10. The method of claim 1 wherein said terminally active polymer comprises polyene mer.
 11. The method of claim 1 further comprising isolating said polymer having terminal functionality and adding it to a composition that comprises one or more particulate fillers.
 12. The method of claim 11 further comprising heating said composition so as to form a vulcanizate.
 13. The method of claim 12 further comprising forming a tire component from said vulcanizate.
 14. The method of claim 1 wherein said cyclic compound has one of the following general formulas:

where each R³ independently is a monovalent organic group or a halogen atom with the proviso that at least one R³ is secondary amine group or a halogen atom.
 15. The method of claim 1 wherein said terminally active polymer is a carbanionic polymer.
 16. The method of claim 15 wherein said polymer further comprises mer that comprise a pendent aromatic group.
 17. The method of claim 16 wherein said polymer comprises random microstructure.
 18. The method of claim 1 wherein said terminally active polymer comprises polyene mer, said method further comprising providing said terminally active polymer from a lanthanide-based catalyst composition.
 19. The method of claim 18 wherein said catalyst system is formed by combining ingredients that comprise a lanthanide compound, an alkylating agent, and a halogen-containing compound.
 20. The method of claim 18 wherein said terminally active polymer has a cis-1,4-linkage content of at least about 90%. 